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Galileo Galilei
for 5/31 – 6/1/16
Read the secondary handout and textbook primary source on p. R56 to complete
this bell.
Primary Source
The Starry Messenger
A. His telescopes
1. How did Galileo construct his
first telescope?
2. What was the first telescope
able to do?
3. What was the second telescope
able to do?
4. What was his third telescope
able to do?
Secondary Source
A. Findings from Telescope Use
1. What could Galileo conclude
after his observations of Jupiter’s
moons?
2. What was Galileo able to
propose for testing (hypothesis)
after observing the phases of the
planet Venus?
3. Ultimately, what could Galileo
conclude from all of his telescope
observations?
DISCOVERIES FROM GALILEO’S TELESCOPES
Galileo did not invent the telescope, but he was the first to make
powerful telescopes with good optics. He was also among the first to train
his telescopes on the sky.
What Galileo saw through his telescope eventually helped show that
Earth was not the center of the universe. Galileo’s observations were
strong evidence for the Copernican theory that Earth and other planets
revolve around the sun. Galileo was first to observe four moons orbiting
the planet Jupiter. He saw these as tiny stars near the equator of the planet,
changing position from night to night. If these bodies revolved around
Jupiter and not Earth, didn’t it stand to reason that other bodies might not
be revolving around Earth either? Galileo also observed the planet Venus
and noticed that it had phases similar to the phases of the moon. However,
Venus appeared equally bright no matter what its phase. Galileo
hypothesized that Venus could not be making a circular orbit around Earth
for this to be true; it had to be much farther away in its full phase and much
closer in its crescent phase. This supported the idea that Venus revolved
around the sun rather than Earth.